It is well known that integrated circuit chips are becoming increasingly complex with correspondingly crowded circuit architectures. However, such crowded architectures often result in an unwanted increase in heat generation. For example, some integrated circuit chips currently generate as much as 40-50 watts of power on a 1-inch by 1-inch surface. The excess heat generated by such chips will destroy or burn-up the chip if not removed. That is, if heat is generated by the chip at a rate of 40-50 Joules per second (40-50 watts), the heat must be dissipated at some rate which enables the chip to remain functional.
The removal of heat from high heat generating integrated circuit chips has be attempted using extremely large heat sinks. However, such prior art heat sinks are typically bulky, unwieldy, and consume valuable printed circuit board real estate. In another attempt to remove excess heat, water or liquid-cooled heat sinks have been employed. Again, such prior art heat sinks are bulky, unwieldy, and consume valuable printed circuit board real estate. Furthermore, liquid cooled heat sink are often prohibitively expensive, extremely complex, and difficult to mass, produce due to reliability problems.
One technique attempted to achieve sufficient heat transfer or dissipation is referred to as impingement cooling. In impingement cooling, a fan is attached to the heat sink. The fan blows or "impinges" air against or over the heat sink attached to an integrated circuit chip. While impingement cooling increases the effectiveness of the heat sink, impingement cooling also has significant drawbacks associated therewith.
With reference now to Prior Art FIG. 1, a prior art heat sink assembly 10 adapted for impingement cooling is shown. Specifically, as shown in Prior Art FIG. 1, heat sink assembly 10 includes a heat sink 12 having a fan 14 attached thereto. The fan heat sink of Prior Art FIG. 1 is for example, a Thermalloy model TCM425 fan heat sink manufactured by the Thermalloy company of Dallas, Tex. The addition of fan 14 significantly increases the cost of heat sink assembly 10. As a further drawback, the addition of fan 14 substantially increases the size and bulkiness of heat sink assembly 10. Furthermore, fan heat sinks are undesirably "tall" or have an especially large "profile." That is, such fan heat sinks extend outward a great distance from the surface of the printed circuit board on which the integrated circuit chip is attached. Thus, a printed circuit board having a fan heat sink attached thereto can only be used in an environment adapted to accommodate the especially large profile of the fan heat sink.
The effectiveness of impingement cooling systems depends on numerous factors. These factors include, for example, the surface area of the heat sink, and the velocity with which air flows through the surface of the heat sink. Unfortunately, in the prior art, heat sinks having a large surface area tend to limit the velocity with which air flows through the heat sink surface. Therefore, in the prior art, increased heat sink surface area is associated with a unwanted decrease in air flow velocity through the surface of the heat sink.
Prior Art FIG. 2 shows heat sink assembly 10 of Prior Art FIG. 1 with fan 14 removed therefrom in order to dearly show the structure of the surface of heat sink 12. As shown in Prior Art FIG. 2, heat Sink 12 is comprised a plurality of pin-shaped fins extending from the surface thereof. Although the pin-shaped fins of heat sink 12 provide significant surface area, the pin-shaped fins significantly restrict and slow the flow of coolant air across the surface of heat sink 12. Thus, in the prior art, coolant air speed has been sacrificed in order to achieve a large surface area. In other instances, the surface area of prior art heat sinks has been sacrificed in order achieve greater air speed.
Thus, a need exists for a heat sink unit or assembly which provides sufficient heat dissipation to effectively cool high heat generating integrated circuit chips. A further need exists for a heat sink unit or assembly which provides substantial surface area without substantially slowing or restricting the flow of coolant air across the surface of the heat sink unit or assembly. It is, therefore, an object of the present invention to provide a heat sink unit or assembly which provides sufficient heat dissipation to effectively cool high heat generating integrated circuit chips. It is a further object of the present invention to provide a heat sink unit or assembly which provides substantial surface area without substantially slowing or restricting the flow of coolant air across the surface of the heat sink unit or assembly.